The bombs that blew up commuter trains in Spain in March 2004, as well as blasts in Bali in October 2002 and Jakarta in August 2003, all relied on cell phones to trigger explosives. It has been widely reported that a cell phone jammer thwarted an assassination attempt on Pakistani President Musharraf in December 2003. When President Bush visited London in November 2004, it was reported that British police considered using signal blocker to protect the president’s motorcade through London. During a hostage situation, police can control when and where a captor can make a phone call. https://www.dojammer.com/cell-phone-jammers.html